1. Field of the Invention
This invention relates to a process for treating sulphur containing ores, and more particularly, is directed to a process for recovering copper, silver and zinc from a partially roasted pyrite concentrate by ferric sulphate leaching.
2. Description of the Prior Art
In the past a variety of processes have been used for the extraction of metals and non-metals from sulphide ores. In many of these processes the sulphide ores have been subjected to concentration steps prior to recovery of specific metal values contained therein. Most of these processes suffer from the same disadvantage, in that they are incapable of recovering all the metal values in the ore using one economical process.
In addition many of the prior art processes have been limited to specific ores and concentrates which have a high concentration of the desired components to make the removal of those components economically feasible.
In a number of the above mentioned processes the sulphide ore concentrates are subjected to ferric sulphate leaching techniques to recover the metal values contained therein. Some of these processes even include a thermal decomposition of the pyrite concentrate prior to leaching. However, in many of these prior art processes the pyrite concentrate matrix is virtually unattacked by the initial heating of the pyrite and therefore a significant portion of the metal values occluded in the pyrite is lost, since they cannot be reached by the leach solution.
Lastly many of the previously mentioned processes require the use of either chloride or cyanide to extract the silver from the pyrite. Chloride ions in an oxidizing atmosphere present corrosion problems and the use of cyanide may involve problems in waste control.
The process of the present invention provides for the recovery of the metal values from a pyrite ore by opening the pyrite matrix prior to the leaching stage resulting in higher percentages of metal extraction.
Furthermore the process of the present invention allows for the complete recovery of essentially all the metal values contained in the pyrite concentrate without the use of chloride or cyanide.